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Lenovo ThinkPad T400s 51J0497 Replacement Battery 11.1V

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From $133.99 USD $160.99
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Fits Lenovo ThinkPad T400s laptop; replaces OEM part numbers 51J0497, 42T4690, 42T4691, 42T4688, 42T4689.
11.1V, 4400mAh lithium-ion cell delivers 48.84Wh to sustain the T400s CPU, display, and wireless through a full workday.
Connector slides into the rear battery bay slot with positive terminals facing the release latch; locking tab secures flush against the chassis.
We bench-tested the cell across three charge cycles; the BMS accepted the EEPROM handshake without fault codes on insertion into a T400s motherboard.
After installation, run one full discharge to hibernation-cutoff then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the inaccurate health warning.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

11.1V

Amp

4400mAh

Lenovo ThinkPad T400s Series — 11.1V Li-ion Replacement Battery (51J0497)

This 11.1V, 4400mAh (48.84Wh) Li-ion battery replaces the original cell in the Lenovo ThinkPad T400s and its sub-variants, including the T400s 2801, 2808, and 2809. It slots into the standard T400s battery bay and connects via the original multi-pin interface. Cross-references OEM part numbers 42T4688, 42T4689, 42T4690, and 42T4691.

  • T400s platform fit: All listed T400s variants share the same 11.1V three-cell rail, battery bay dimensions, and BMS handshake protocol — which is why one part number covers the full sub-variant range without modification.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a T400s unit, confirmed BMS communication across all charge states, and verified the pack holds voltage through CPU and display load without triggering an early cutoff.
  • Post-install calibration on the T400s: After fitting, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting poor battery health immediately after replacement

The ThinkPad BIOS stores battery health data in EEPROM on the battery's internal circuit board. When a new cell is installed, the BIOS reads stale or mismatched EEPROM data and flags the pack as degraded before it has run a single cycle. This is not a fault with the replacement cell — it is a calibration state. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% triggers the BIOS learn cycle and rewrites the health register. After two to three full cycles, the health indicator should read normal.

T400s shutting down at 20–30% charge shown on the gauge

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge reports 25% remaining while the cell is already near its low-voltage cutoff under combined CPU and display load — the sudden draw exposes the mismatch and triggers an immediate shutdown. The fix is the same calibration cycle: discharge fully to hibernate, then charge to 100% without interruption. After two full cycles, the fuel gauge IC recalibrates its endpoint references and the shutdowns stop. If the problem persists after three cycles, check that the BIOS battery charge threshold is not set below 95% in Lenovo Power Manager.

Compatible Models

ThinkPad T400s ThinkPad T400s 2801 ThinkPad T400s 2808 ThinkPad T400s 2809 ThinkPad T400s 2815 ThinkPad T400s 2823 ThinkPad T400s 2824 ThinkPad T400s 2825 ThinkPad T410s

Replaces Part Numbers

51J0497 42T4690 42T4691 42T4688 42T4689

Technical Specifications

Voltage11.1V
Amp Hours4400mAh
Capacity4400mAh
Rate48.84Wh
Net Weight290.9g /10.26 oz
Gross Weight550.9g /19.43 oz
Approximate Weight550.9g /19.43 oz
Dimension 261.80 x 73.55 x 12.76mm

Product Highlights

  • Brand: Lenovo
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My T400s shows the replacement battery as "0%" and won't read it at all — is the cell dead out of the box?

The ThinkPad BIOS pulls capacity data from the battery's EEPROM, and a new cell that has never been cycled can return a null or zero reading on the first boot. Remove the battery, reseat it firmly, then boot into Windows and let the gauge settle for two minutes. If it still reads 0%, plug in AC power and leave the battery to charge uninterrupted for 90 minutes — the BMS will initialise fully once the cell voltage crosses the BIOS recognition threshold, typically around 10.8V.

The T400s fuel gauge jumps around wildly — showing 60%, then 85%, then 45% within minutes — what causes that?

The fuel gauge IC on the T400s motherboard maps percentage to voltage using calibration data from the previous cell. A new cell with a slightly different discharge curve makes the IC interpolate incorrectly until it has mapped the full voltage range of the replacement pack. Run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. Repeat twice. After three complete cycles the gauge IC recalibrates its reference points and the readings stabilise.

Power Manager is showing the new battery's capacity as 28Wh when the pack is rated 48.84Wh — is that a faulty unit?

The Wh figure shown in Power Manager is read from the battery's EEPROM, which may report the rated design capacity of the original OEM cell rather than the actual chemistry of the replacement. This is a firmware reporting difference, not a cell fault — the pack still stores and delivers the full 48.84Wh. Cycle the battery fully twice; some ThinkPad BIOS versions update the displayed Wh value after the learn cycle completes. If the figure remains mismatched, cross-check actual discharge time against expectations — if run time is correct, the Wh display can be disregarded.

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